Decoupling by local random unitaries without simultaneous smoothing, and applications to multi-user quantum information tasks

Understand

We show that a simple telescoping sum trick, together with the triangle inequality and a tensorisation property of expected-contractive coefficients of random channels, allow us to achieve general simultaneous decoupling for multiple users via local actions.

• Employing both old [Dupuis et al.
• Commun.
• Math.